The purpose of the contract is to test 10 chemicals per year for mutagenicity using the Drosophila sex-linked recessive lethal assay. This assay is an in vivo test for germ cell mutation. Chemicals will be administered first by feeding. If the result is negative, the chemical will be administered by injection and retested. If the result is positive in either test for recessive lethals, the chemical will be tested in the assay for reciprocal translocations using the route administration that gave the positive result. The chemicals will be chosen based on an interest in the results of the two year assay for carcinogenesis or the mouse germ cell mutagenesis assays.